The present disclosure relates generally to power supplies for microelectromechanical systems (MEMS) and, more particularly, to a micro power supply with integrated charging capability.
With the development of microelectronic fabrication methods for manufacturing microelectromechanical systems (MEMS) devices, such as microminiature motors, actuators, sensors, etc. in silicon wafers, there has developed a need for micro power supplies to provide the power to operate these devices. Conventional small button cells or similar small batteries are currently used to meet these power needs. Recently, a new technology has been developed to fabricate microbatteries using conventional silicon microelectronic processing techniques. Nixe2x80x94Zn microbatteries have been produced by chemical processing steps employing a combination of photolithographic techniques, wet and dry chemical etching methods, rinsing steps, and thermal evaporation of metal contacts.
While these microbatteries are fully integrateable in a silicon wafer, they offer limited capacity as a primary battery. However, as secondary batteries, they have the capability of being recharged. The present techniques for recharging the microbatteries involve using a power source located externally with respect to the silicon wafer. Unfortunately, this limits the ultimate miniaturization of a micro power supply incorporating microbatteries.
The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by micro power supply. In an exemplary embodiment, the micro power supply includes a microbattery formed within a substrate and an energy gathering device for capturing energy from a local ambient environment. An energy transforming device is also formed within the substrate for converting energy captured by the energy gathering device to electrical charging energy supplied to the microbattery.
In a preferred embodiment, the energy gathering device is also formed within the substrate. A fuzzy-logic based charge controller device is further formed within the substrate for controlling the flow of charging current and output voltage from the energy transforming device to the microbattery. The charge controller device selectively couples the energy transforming device to the microbattery through switching of a pulse width modulation circuit.
In another embodiment, an integrated, rechargeable micro power supply for a microelectromechanical system (MEMS) includes a microbattery formed within a semiconductor substrate, and a solar cell, formed within the substrate, for capturing light energy from a local ambient environment. The solar cell converts the light energy into electrical charging energy to be supplied to the microbattery. A charge controller device is also formed within the substrate, and selectively couples the solar cell to the microbattery.